Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 220332
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
832 PM PDT THU AUG 21 2014

.DISCUSSION...CURRENT TEMPERATURES ARE SEVERAL DEGREES WARMER
THAN YESTERDAY AT THIS TIME AND DEW POINT TEMPERATURES ARE MUCH
LOWER THAN YESTERDAY...INDICATING A VERY DRY AIR MASS IN IN PLACE.
A DRY COLD FRONT IS MOVING THROUGH THE FORECAST AREA THIS
EVENING...AND THIS WILL LOWER TEMPERATURES TOMORROW...TO READINGS
ABOUT 5 DEGREES BELOW NORMAL. GUSTY WINDS ARE IMPACTING THE AREA
TODAY IN THIS DRY AIR MASS...AND THIS IS INVIGORATING FIRE
BEHAVIOR IN THE REGION...WITH SMOKE BEING OBSERVED ON SATELLITE
IMAGERY OVER WESTERN SISKIYOU COUNTY AND OVER THE CASCADES.

THE COAST...COASTAL VALLEYS...AND UMPQUA BASIN WILL BE AFFECTED BY A
STRONG MARINE PUSH AND STRATUS CLOUDS TONIGHT INTO TOMORROW
MORNING...WHICH SHOULD LINGER INTO THE AFTERNOON. FARTHER
INLAND...TONIGHT WILL BE ANOTHER COOL AND CLEAR NIGHT. TEMPERATURES
WILL BE COOLER TOMORROW AND WINDS WILL BE GUSTY AGAIN..SHIFTING TO A
MORE NORTHWEST DIRECTION...WITH CONTINUED TIGHT PRESSURE GRADIENTS
ACROSS THE FORECAST AREA. A GENERAL WARMING AND DRYING TREND WILL
BEGIN ON SATURDAY FOR THE FORECAST AREA. A THERMAL TROUGH WILL
ACCOMPANY THE WARMING AND RESULT IN DRY CONDITIONS OVERNIGHT ON
HIGHER TERRAIN IN SISKIYOU COUNTY...AFFECTING FIREFIGHTING
CONDITIONS THERE.

PLEASE SEE THE PREVIOUS DISCUSSION BELOW FOR DETAILS ABOUT THE
WEEKEND WEATHER AND BEYOND.


&&

.AVIATION...STRATUS WITH MVFR AND IFR CIGS IS MOVING INTO THE
COAST NOW AND IS EXPECTED TO MAKE ITS WAY INLAND TO THE UMPQUA
BASIN TONIGHT. STRATUS WILL BURN OFF TO VFR BY MID MORNING AT THE
COAST...RETURNING BY THE EVENING. ADDITIONALLY...SMOKE FROM NEARBY
WILDFIRES WILL REDUCE VISIBILITY MAINLY IN SISKIYOU COUNTY.
ELSEWHERE, VFR CONDITIONS WILL PERSIST FOR THE NEXT 24 HOURS.

&&

.MARINE...UPDATED 230 PM PDT THU 22 AUG 2014...WINDS AND SEAS HAVE
ALREADY DECREASED AND WILL DECREASE FURTHER AS A WEAK FRONT MOVES
THROUGH THE WATERS TONIGHT AND FRIDAY MORNING. HOWEVER, HIGH
PRESSURE WILL BUILD IN BEHIND THE FRONT AND A THERMAL TROUGH WILL
DEVELOP INLAND LATER FRIDAY, RESULTING IN A RETURN OF NORTH WINDS
AND WIND DRIVEN SEAS WHICH WILL LAST THROUGH AT LEAST TUESDAY. THE
STRONGEST WINDS AND STEEPEST SEAS WILL BE OVER THE SOUTHERN OUTER
WATERS SOUTH OF GOLD BEACH DURING THE AFTERNOONS AND EVENINGS EACH
DAY. WINDS AND SEAS MAY BOTH DROP BELOW SMALL CRAFT ADVISORY
LEVELS LATE AT NIGHT THROUGH EARLY MORNING. -WRIGHT


&&

.PREV DISCUSSION... /ISSUED 311 PM PDT THU AUG 21 2014/

SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...A WEAK COLD FRONT IS
NOW MOVING INTO THE OREGON COASTAL WATERS AND WILL BRING AN
ONSHORE PUSH OF COOLER AIR AND LOW CLOUDS TONIGHT INTO FRIDAY
MORNING. THE STRATUS WILL THICKEN ALONG THE COAST LATE THIS
EVENING THEN SPREAD INTO THE UMPQUA BASIN LATE TONIGHT. THIS
SCENARIO IS SIMILAR TO WHAT TRANSPIRED ON WEDNESDAY MORNING WITH
THE MARINE LAYER EXPECTED TO BE DEEP ENOUGH FOR SCATTERED LOW
CLOUDS TO EXTEND OVER THE UMPQUA DIVIDE INTO THE ILLINOIS VALLEY
AND PERHAPS FAR NORTHERN ROGUE VALLEY FOR A COUPLE HOURS AROUND
SUNRISE. THE ASSOCIATED UPPER LEVEL TROUGH IS NOW OVER NORTHERN
WASHINGTON AND WILL MOVE TO EASTERN OREGON ON FRIDAY. BY REMAINING
ON THE BACK SIDE OF THE TROUGH, OUR AREA WILL BE UNDER A COOL,
DRY, AND STABLE AIR MASS. HIGH TEMPERATURES ON FRIDAY WILL BE
MAINLY 3 TO 5 DEGREES COOLER THAN TODAY, AND IT WILL LIKELY BE THE
COOLEST DAY OUT OF THE NEXT 7 DAYS.

A MODERATE TO STRONG OFFSHORE FLOW PATTERN WILL DEVELOP FRIDAY
NIGHT WITH WARM AND DRY WEATHER...ESPECIALLY OVER FOOTHILLS AND RIDGES.
HIGH TEMPERATURES WILL BE MAINLY A FEW DEGREES ABOVE NORMAL ON
SATURDAY AS A THERMAL TROUGH WILL DEVELOP OVER NORTHERN
CALIFORNIA FRIDAY NIGHT, EXTEND TO THE SOUTHERN OREGON COAST EARLY
SATURDAY THEN STRENGTHEN INTO SUNDAY AND PUSH INLAND FOR A COUPLE
DEGREES OF ADDITIONAL WARMING SUNDAY AFTERNOON. THE WARMING WILL
BE MOST NOTICEABLE NEAR BROOKINGS WITH OFFSHORE FLOW PRODUCING
DOWNSLOPE WARMING.

LONG TERM...MONDAY THROUGH THURSDAY...AN UPPER LEVEL TROUGH WILL
TRACK SOUTHEAST FROM BRITISH COLUMBIA INTO WESTERN MONTANA ON
MONDAY. THIS WILL RESULT IN GUSTY NORTH TO NORTHWEST WINDS MONDAY
AFTERNOON THAT WILL BE STRONGEST EAST OF THE CASCADES, AND ALSO
SHAVE A COUPLE DEGREES OFF OF HIGH TEMPERATURES COMPARED TO THOSE
OF SUNDAY. THE INFLUENCE OF THE TROUGH WILL BE FLEETING WITH A
STRONG RIDGE OF HIGH PRESSURE EXPECTED TO PUSH TO THE WEST COAST
ON TUESDAY THEN INLAND ON WEDNESDAY. TUESDAY AND WEDNESDAY WILL BE
HOT AND SUNNY DAYS.

THERE IS A POSSIBILITY THAT THE MODELS ARE TOO PROGRESSIVE, BUT THE
12Z GFS AND ECMWF MODELS HAVE COME INTO BETTER AGREEMENT THAT
AN UPPER LEVEL TROUGH WILL MOVE SOUTHEAST INTO BRITISH COLUMBIA ON
THURSDAY AND WEAKEN THE RIDGE AND BRING A RETURN OF A WESTERLY
FLOW ALOFT WITH SEVERAL DEGREES OF COOLING. THIS WOULD STILL BE A
STABLE PATTERN AND HIGH TEMPERATURES WOULD STILL BE A FEW TO
SEVERAL DEGREES ABOVE NORMAL.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FOR WINDS FROM 5 PM FRIDAY TO 11 PM PDT
     TUESDAY FOR PZZ376.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 5 PM FRIDAY TO 11
     PM PDT TUESDAY FOR PZZ376.

$$

NSK/DW/TRW





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